From 12b9d7ccb841805e347fec8f733f368f43ddba40 Mon Sep 17 00:00:00 2001 From: Mathieu Desnoyers Date: Wed, 1 Jul 2009 17:37:22 -0400 Subject: x86: Fix fixmap page order for FIX_TEXT_POKE0,1 Masami reported: > Since the fixmap pages are assigned higher address to lower, > text_poke() has to use it with inverted order (FIX_TEXT_POKE1 > to FIX_TEXT_POKE0). I prefer to just invert the order of the fixmap declaration. It's simpler and more straightforward. Backward fixmaps seems to be used by both x86 32 and 64. It's really rare but a nasty bug, because it only hurts when instructions to patch are crossing a page boundary. If this happens, the fixmap write accesses will spill on the following fixmap, which may very well crash the system. And this does not crash the system, it could leave illegal instructions in place. Thanks Masami for finding this. It seems to have crept into the 2.6.30-rc series, so this calls for a -stable inclusion. Signed-off-by: Mathieu Desnoyers Acked-by: Masami Hiramatsu Cc: LKML-Reference: <20090701213722.GH19926@Krystal> Signed-off-by: Ingo Molnar --- arch/x86/include/asm/fixmap.h | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) (limited to 'arch') diff --git a/arch/x86/include/asm/fixmap.h b/arch/x86/include/asm/fixmap.h index 3eb0f79a532..7b2d71df39a 100644 --- a/arch/x86/include/asm/fixmap.h +++ b/arch/x86/include/asm/fixmap.h @@ -111,8 +111,8 @@ enum fixed_addresses { #ifdef CONFIG_PARAVIRT FIX_PARAVIRT_BOOTMAP, #endif - FIX_TEXT_POKE0, /* reserve 2 pages for text_poke() */ - FIX_TEXT_POKE1, + FIX_TEXT_POKE1, /* reserve 2 pages for text_poke() */ + FIX_TEXT_POKE0, /* first page is last, because allocation is backward */ __end_of_permanent_fixed_addresses, /* * 256 temporary boot-time mappings, used by early_ioremap(), -- cgit v1.2.3